IDENTIFICATION OF CELL-BINDING SITES IN THE LAMININ ALPHA-1 CHAIN CARBOXYL-TERMINAL GLOBULAR DOMAIN BY SYSTEMATIC SCREENING OF SYNTHETIC PEPTIDES

The laminin al chain carboxyl-terminal globular domain has been identi fied as a site of multiple biological activities. Using a systematic s creening for cell binding sites with 113 overlapping synthetic peptide beads that covered this domain, we found 19 potential active sequence s. Corresponding synthetic peptides were evaluated for direct cell att achment, spreading, and inhibition of cell spreading to a laminin-1 su bstrate using several cell lines. Five peptides (AG-10, AG-22, AG-32, AG-56, and AG-73) showed cell attachment activities with cell-type spe cificities. Cell spreading on AG-10 was inhibited by beta 1 and alpha 6 integrin antibodies and on AG-32 was inhibited by beta 1, alpha 2, a nd alpha 6 integrin antibodies. In contrast, cell adhesion and spreadi ng on peptide AG-73 were not inhibited by these antibodies. The minimu m active sequences of AG-10, AG-32, and AG-73 were determined to be SI YITRF, IAFQRN, and LQVQLSIR, respectively. These sequences are highly conserved among the different species and different laminin alpha chai ns, suggesting that they play a critical role for biological function and for interaction with cell surface receptors.